Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
000
FXUS02 KWBC 231610
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1209 PM EDT TUE AUG 23 2016

VALID 12Z FRI AUG 26 2016 - 12Z TUE AUG 30 2016

...PATTERN OVERVIEW...

SUB-TROPICAL RIDGING WILL HOLD STRONG OVER THE SOUTHERN
MID-ATLANTIC STATES LATE THIS WEEK AND THROUGH THE WEEKEND...WHILE
GENERAL TROUGHING WILL PERSIST IN THE WESTERN U.S..  WITHIN THE
MEAN FLOW...SHORTWAVE ENERGY LIFTING NORTH OF THE GREAT LAKES ON
FRIDAY WILL HELP PUSH A COLD FRONT THROUGH THE NORTHEAST...BEFORE
THE TAIL END OF THE BOUNDARY STALLS AND WEAKENS WHILE TRYING TO
PRESS INTO THE STRONG RIDGING OVER THE SOUTHERN MID-ATLANTIC
STATES THIS WEEKEND.  UPSTREAM SHORTWAVES COULD ALSO TRACK THROUGH
THE LOWER 48 THIS WEEKEND...ONE CROSSING THE NORTH CENTRAL U.S.
AND SECOND DROPPING TROUGH BRITISH COLUMBIA...BUT THE DETAILS OF
THESE FEATURES REMAIN UNCERTAIN.  ALSO OF NOTE...THE NATIONAL
HURRICANE CENTER IS CURRENTLY MONITORING AN AREA OF SHOWERS AND
THUNDERSTORMS EAST OF THE LEEWARD ISLANDS WHICH COULD POTENTIALLY
IMPACT THE SOUTHEASTERN U.S. EARLY NEXT WEEK.


...UNCERTAINTY ASSESSMENT/MODEL PREFERENCES...

THE GREATEST AREA OF UNCERTAINTY CONTINUES TO BE WITH THE
EVOLUTION OF FLOW FROM ALASKA TO THE NORTHWESTERN U.S. THIS
WEEKEND.  ENSEMBLE MEANS HAVE COME INTO BETTER AGREEMENT ACROSS
THE REGION...BUT THERE REMAINS AN UNUSUALLY LARGE AMOUNT OF SPREAD
BETWEEN DETERMINISTIC RUNS AND INDIVIDUAL ENSEMBLE MEMBERS TO
SUGGEST THIS IS STILL A LOW CONFIDENCE FORECAST.  A SECOND AREA OF
FORECAST UNCERTAINTY IS WITH THE POSSIBLE TROPICAL SYSTEM
APPROACHING THE SOUTHEASTERN U.S. THIS WEEKEND/EARLY NEXT
WEEK...ESPECIALLY SINCE THE SLIGHTEST DIFFERENCE IN TRACK AND
STRENGTH WILL HAVE A LARGE IMPACT ON THE SENSIBLE WEATHER.  THE
WPC FORECAST STARTED WITH A GENERAL CONSENSUS BLEND OF THE
GFS/ECMWF...BUT THEN TRANSITIONED TO ENSEMBLE MEAN GUIDANCE LATER
IN THE FORECAST PERIOD TO ACCOUNT FOR THE UNCERTAINTY OVER THE
GULF OF ALASKA/WESTERN CANADA/NORTHWESTERN U.S. AND SOUTHEASTERN
U.S..


...WEATHER HIGHLIGHTS...

SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE WITH THE COLD FRONT
PRESSING THROUGH THE NORTHEAST ON FRIDAY...BUT THEN THE CHANCE FOR
PRECIPITATION DIMINISHES AS THE BOUNDARY WEAKENS OVER THE
MID-ATLANTIC STATES THIS WEEKEND.  SHOWERS AND THUNDERSTORMS WILL
ALSO BE POSSIBLE ACROSS THE MIDDLE TO UPPER MISSISSIPPI VALLEY
THIS WEEKEND...AHEAD OF THE SHORTWAVE CROSSING THE NORTH CENTRAL
U.S..  FINALLY...HEAVY RAINS COULD THREATEN PORTIONS OF THE
SOUTHEASTERN U.S. BY EARLY NEXT WEEK...DEPENDING ON THE DETAILS OF
THE POTENTIAL TROPICAL SYSTEM.  PLEASE REFER TO THE NATIONAL
HURRICANE CENTER FOR THE LATEST INFORMATION ON THIS FEATURE
(WWW.NHC.NOAA.GOV).


GERHARDT


$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.